1. Field of the Invention
The present invention relates to polyolefins having an additive that gives it flame retardant and abrasion resistance properties. More specifically, the present invention relates to a method for chemically grafting polymers having flame retardancy and abrasion resistance additives incorporated into them to polyolefms such that they are covalently bound to the substrate polymer. The resulting material has superior mechanical, flame retardancy and abrasion resistance properties.
2. Prior Art
Polyolefins are synthetic organic thermoplastics that are composed of carbon and hydrogen and as such, are inherently flammable. Applications incorporating polyolefins, such as pallets, construction, transportation, electrical, home furnishings, toys, outdoor play equipment, industrial tanks, containers, materials handling equipment and housewares, demand compliance with mandatory flame retardancy requirements, thereby requiring the addition of flame retardant additives.
A variety of flame retardant additives have been developed specifically for treatment of polyolefins to hinder ignition and reduce flame spread so the polyolefin can meet the required flammability specifications. Typically, most additive type flame retardants are incompatible with the polymer matrix and lead to detrimental mechanical and physical effects which are demonstrated by an observable loss in physical property attributes, particularly impact strength. The usual result is a compromise between deteriorated physical properties and the desired enhancement of combustion resistance.
In flame retarding thermoplastics, the synergistic action between organohalogen compounds and metal oxides is well known. A wide variety of organic, halogenated compounds are used as additives in conjunction with metal oxides, especially those having metals of Groups III, IV, V and VI. Unfortunately, addition of these flame retardant compounds has a deleterious effect on mechanical and physical properties of polyolefins such as polyethylene and polypropylene.
Recently, there has been research into derivatives of polyethylene and polypropylene. These polyolefins may be modified so that they have various functional groups or organic molecules incorporated into them. These methods, however, have not yet produced materials having acceptable levels of flame retardancy. In addition, these modifications to the polyolefins require several additional processing steps. This increases the time, difficulty and expense of the end product.
Adedeji et al. (Publication No. US 2001/0031807) to General Electric, discloses plastic pallets of resins such as polyphenylene or polycarbonate resin. It is also suggested that a commercially available flame retardant agent may be added to the composition. The pallets are said to meet the UL2335 protocol.
Falcone et al. (Publication No. US 202/0019466) discloses phosphoramides and mixtures thereof with thermoplastic resins which might further include halogen-containing flame retardants such as brominated flame retardants. It does not disclose polyolefins having graft polymers with incorporated flame retardants.
Horne (U.S. Pat. No. 4,230,049) discloses pallets and platforms comprised of composites formed of cellulose fibers reinforced with cross-linked polyethylene or polypropylene.
Ishida et al. (U.S. Pat. No. 4,397,246) discloses synthetic pallets composed of resins such as polyethylenes or polypropylenes.
Horne (U.S. Pat. No. 4,467,728) discloses a composite structural material which includes a starting polymer of polyethylene. It does not disclose polyolefins having graft polymers with incorporated flame retardants.
Campbell et al. (U.S. Pat. No. 6,228,912) discloses resin compositions such as polyethylene and polypropylene which may include flame retardants such as those including bromine. It does not disclose polyolefins having graft polymers with incorporated flame retardants.
To date there is no ideal flame retardant commercially available. They all have detrimental effects on the physical properties of the polymer they are incorporated in. It would, therefore, be desirable to provide a highly flame retardant, impact resistant and abrasion resistant polyolefin as well as a method for imparting flame retardance and improved impact resistance to polyolefin compositions in which the additives are uniformly dispersed throughout the composition.